Two important technologies for imaging microscopic features, particularly on a generally planar substrate such as an integrated circuit, include atomic force microscopy (AFM) and microwave impedance microscopy. In AFM, a nanometer-scale probe tip is dragged or tapped along a surface and its deflection is measured to thereby determine the topography of the surface, that is, to image its physical contour. In microwave impedance microscopy, for example, as explained by Kelly et al. in U.S. Pat. No. 7,190,175, incorporated herein by reference, a microwave probe is scanned over the surface of a sample and the microwave (electrical) impedance of the sample is measured to thereby image the impedance of the sample, for example, the pattern of conductive interconnects on a dielectric layer for which the physical contour is not of primary importance. In some implementations, the microwave probe is imbedded in a dielectric pad to protect it from damage during scanning contact, but the geometry decreased the resolution of the microwave measure. On the other hand, exposed microwave probes dragged along a surface are subject to erosion and the wear decreases their lifetimes. Conventional microwave probes also suffer from low signal-to-noise.